用Sol-Gel法制备粉料及KTN陶瓷烧结研究

研究了用Ｓｏｌ－Ｇｅｌ法制备粉料和气氛烧结ＫＴＮ陶瓷的优化工艺．通过分析烧结气氛和烧结条件对ＫＴＮ陶瓷性能的影响,指出相应的最佳烧结温度为１２００℃、保温时间为８７ｈ．     

Sol–gel processing of IrO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript> mixed metal oxides based on an iridium acetate precursor

Mixed IrO₂–TiO₂ oxides were prepared by the sol–gel method by adding an aqueous solution of an iridium(III) acetate precursor [Ir₃O(OAc)₆ (HOAc)₃]OAc, to titanium tetraethoxide in ethanol. By using an acetylacetonate modifier to stabilize the hydrolysed titanium alkoxide and by omitting a catalyst, gels were produced in all cases. Transmission electron microscopy and EDX analysis confirmed the high dispersion of iridium in the dried gel material on the nanometre scale. The images also show spherical cage features up to 20 nm in diameter. High mass losses of the gels in the TGA scans suggested low degrees of hydrolysis of the acetate precursor, but calcination gave a crystalline, mixed oxide (Ti_xIr_1–xO₂) solid solution. The precursor is also soluble in ethanol, which provides a slightly modified route to similar materials.     

Sol‐Gel‐Derived Biosensor Based on Plant Tissue: The Inhibitory Effect of Atrazine on Polyphenol Oxidase Activity for Determination of Atrazine

This work presents a sol‐gel based biosensor for atrazine determination which has been obtained by introducing the enzyme polyphenol oxidase from apple tissue in a sol‐gel matrix. Apple tissue acts as a molecular recognition element. Atrazine is an inactive compound electrochemically; redox coupling of dopamine was used for studying atrazine behavior. Atrazine was determined by monitoring the inhibition power of polyphenol oxidase activity. The measurements were performed in 0.1 M KH₂PO₄‐NaOH buffer (pH 7.5). The effect of various experimental parameters such as pH, concentration of buffer, concentration of dopamine, incubation time and matrix composition has been investigated for optimum analytical performance. The biosensor consisted of 10.3% (w/w) of apple tissue. The bioelectrode exhibits a linear response for dopamine and atrazine concentrations in the range of 5.66 × 10^?6?2.27 × 10^?3M and 1 × 10^?5 ?1 × 10^?4 M with a detection limit of 4.2 × 10^?6 and 5.5 × 10^?6 M, respectively. A correlation coefficient of 0.9945 and a relative standard deviation (R.S.D.) of 3.29% for dopamine, 0.9944 and 3.69% for a trazine were achieved.     

Preparation and characterizat ion of polypropylene/silica composite particl e with interpenetrating network via hot emulsion sol–gel approach

A novel interpenetrating structural ultrafine polypropylene-silica nanocomposite particles were synthesized by a modified sol–gel approach in the presence of the melt polypropylene emulsion. A series of samples with different polypropylene content was prepared to investigate the unique characteristics of this original nanocomposite. The thermal gravimetric analysis and differential scanning calorimetry results showed that the nanocomposites had the interpenetrating structure and good thermal stability,and the crystallization behavior of polypropylene was confined by the silica matrix. The interpenetrating structure of nanocomposites was also suggested by the nitrogen adsorption–desorption measurement results. The scanning electronic microscope and transmission electron microscopy images indicated that the nanocomposites had irregular particle morphology. The nanoparticle tracking analysis results show that the mean size of the nanocomposites was around 160 nm. According to the results obtained from different measurements,a reasonable formation mechanism was proposed.     

Sol–gel coating of poly(ethylene glycol)‐grafted multiwalled carbon nanotubes for stir bar sorptive extraction and its application to the analysis of polycyclic aromatic hydrocarbons in water

Poly(ethylene glycol) grafted onto carboxyl‐terminated multi‐walled carbon nanotubes were prepared by the sol–gel technique as a stationary phase for stir bars. The analytical methodology included stir bar sorptive extraction with micellar desorption followed by liquid chromatography. Polycyclic aromatic hydrocarbons were used as the model compounds to evaluate the extraction performance. The extraction efficiency, for the determination of polycyclic aromatic hydrocarbons from water samples, was optimized based on a chemometrics approach. The effect of the experimental parameters on the extraction response was investigated and the optimum extraction conditions were selected. Under the optimum conditions, the proposed method showed a good linearity within the different ranges for different analytes (e.g. 0.05–500 ng/mL for phenanthrene), a square of the correlation coefficient was higher than 0.999, and an appropriate limit of detection in the range of 0.013–0.072 ng/mL. The recoveries in all cases were above 94%, with relative standard deviations below 2.4%.     

Critical exponents in a percolation picture of the fluorescence quenching during the sol-gel transition

Herewith we report on the measurements of the time evolution of the fluorescence yield and the Rayleigh scattering, performed during the gelation process in the following solutions: gelatin in water, gelatin in a heavy water and agarose in water. Our results provide the experimental evidence of the universal power law, resulting from the percolation theory, which expresses the dependence of the fluorescence yield on the number of intermolecular bonds created during the sol-gel transition. The values of universal critical exponents present in this law are found to have the same values for all investigated materials. Received 4 May 2000     

溶胶-凝胶法制备丙烯酸甲酯-衣康酸酐共聚物/SiO_2杂化材料

以丙烯酸甲酯（ ＭＡ） 和衣康酸酐（Ｉｔｎ） 的无规共聚物和原硅酸四乙酯（ＴＥＯＳ） 作为有机相与无机相前驱体,以３ 氨丙基三乙氧基硅烷（ＡＰＴＥＳ） 为偶联剂,通过溶胶 凝胶过程制备出有机 无机杂化材料．并通过ＳＥＭ、ＤＳＣ 等方法考查了偶联剂用量对所得材料结构及性能的影响．     

香豆素和若丹明在SiO2混合染料凝胶基质中的发光光谱

实验发现,在凝胶材料SiO2中掺杂混合染料香豆素102和若丹明6G后,其光谱比只掺杂单一染料的光谱展宽,两种掺杂染料之间存在能量转换。本文就样品制备和测量结果进行分析。